Fyzikální ústav Akademie věd ČR

Seminar Tuesday, 18 May 2010 - 15:00 - 16:00

Speakers: Katarzyna Roszak
Place: Main lecture hall
Organisers: Department of Condensed Matter Theory

Abstract:
We study the tunneling through a quantum dot coupled to two leads in the situation when the Fermi energy of the emitter lead is similar to the energy level(s) of the quantum dot. The scattering of the emitter lead electrons on an electron inside the dot leads to singular behavior of the current through the quantum dot at resonance and power-law dependence of the current away from resonance (the Fermi edge singularity [1, 2]). As shown in recent experiments [3, 4], noise at such a Fermi edge singularity displays characteristic behavior which cannot be accounted for by Markovian theory.
We have found that the inclusion of non-Markovian effects [5] allows us to account for all of the qualitative features of the noise. In the case of a single level quantum dot, reproducing the current is not sufficient to get quantitative agreement between theory and experiment for the noise; the energy dependence of the noise must be taken into account to acquire a proper fit. This ambiguity is lifted when magnetic field is applied in the experimental setup [4]. Then the two Zeeman split levels in the quantum dot both display Fermi edge singularities and reproducing the energy dependence of the current fixes all the fitting parameters. Nonetheless, the non-Markovian theory for the noise leads to quantitative agreement with experimental data in this case.

[1] G. D. Mahan, Phys. Rev. 163, 612 (1967).
[2] D. A. Abanin and L. S. Levitov, Phys. Rev. Lett. 94, 186803 (2005).
[3] N. Marie, F. Hohls, T. Ludtke, K. Pierz, and R. J. Haug, Phys. Rev. B 75, 233304 (2007).
[4] N. Ubbelohde, F. Hohls, N. Marie, and R. J. Haug, Bidirectional tunneling at a Fermi-edge singularity, unpublished (2010).
[5] C. Flindt, T. Novotny, A. Braggio, and A.-P. Jauho, arXiv:1002.4506 (2010).